Method for alternately constructing underground vertical members using top-down construction method

ABSTRACT

The present invention is provided to shorten a period of underground frame construction in top-down construction method, and more specifically, provides a construction method for alternately constructing underground vertical members downward to lower levels and then constructing remaining vertical members during the same time period after mat and foundation construction, thus making it possible to shorten a construction period of the vertical members and an overall construction period. The method includes a first step of installing the earth retaining wall, constructing the underground pillar post, excavating the first underground level, and constructing the first above-ground level floor; a second step of first constructing the core part of one underground level while constructing the underground level slab downward to support the above-ground level core part which is constructed upward; a third step of alternately constructing an underground vertical member downward; and a step of constructing remaining underground vertical members during the same time period after the construction of the lowest level mat or the foundation, in which the construction period of the underground vertical member is shortened, and thereby the above-ground frame and finishing construction can be started early and an overall construction period is shortened.

TECHNICAL FIELD

The present invention is provided to shorten a period of undergroundframe construction in top-down construction method, and morespecifically, provides a construction method for alternatelyconstructing underground vertical members downward to lower levels andthen constructing remaining vertical members during the same time periodafter mat and foundation construction, thus making it possible toshorten a construction period of the vertical members and an overallconstruction period.

BACKGROUND

The top-down construction method is a construction method for shorteningthe construction period by constructing frames on the above-groundlevels while forming the frames downward to the underground levels.

The general order of the top-down construction method for theunderground level includes installing an earth retaining wall andpillars, excavating each level, and then constructing the last lowestfoundation or mat while constructing a slab downward to have a depth of4th to 7th underground levels.

Among the underground vertical members, the piles (pillar posts) areconstructed at an initial stage of construction, a core part of oneunderground level is constructed for the frame construction of theabove-ground level (superstructure), and the remaining vertical membersare constructed in order (from a lower level to an upper level) afterplacing the foundation or the mat.

At this time, although the frame construction of the above-ground levelis constructed during the same time period with the underground level,the number of levels that go up before the foundation and matconstruction, and the number of levels that go up until the completionof the construction of the underground vertical members are structurallylimited. For example, construction constraint conditions are given inwhich construction of the slab only up to the 8th level is allowed untilthe foundation and the mat are placed, construction of the slab only upto the 15th level is allowed until construction of the undergroundvertical members is completed, and construction of the roof level isallowed without restrictions after construction of the undergroundvertical members is completed.

Therefore, if the frame construction period of the underground levelincreases, the above-ground level frame has to be constructed only up tothe 8th or 15th level, and then the construction stops and waits.Conversely, if the frame construction of the underground level isaccelerated, the frame construction of the above-ground level will alsobe accelerated, so that the overall construction period is greatlyaffected by the underground level work.

In particular, for the construction of the above-ground level frame, ittakes 6 to 7 days for one level to construct one reference level, sothat more than four levels are constructed in one month, but for theconstruction of the underground level frame, it takes 1.5 or 2 monthsfor one level, so that a construction speed of the underground level isrelatively slow.

The problems in the conventional top-down construction method are asfollows.

The conventional construction order of the underground constructionincludes constructing the earth retaining wall, the post, excavation ofeach level down, slab construction of each level, foundation or matconstruction of the lowest level, and the construction of theunderground vertical members upward in a sequence.

Here, the underground vertical member has a feature that it proceeds ina sequence (construction from the lower level to the upper level) afterthe foundation or the mat is placed. The construction period of theunderground vertical members takes 20 to 25 days for one level, so thatit takes 4 to 5 months for the six underground levels.

The underground vertical members are constructed in a sequence(down-top) after the foundation or the mat is placed. Since theabove-ground level can continue to go up after the underground verticalmembers are completed, the underground vertical member is a criticalpath that determines the construction period.

On the other hand, the construction speed of the construction of theabove-ground level frame is fast, with a cycle of 6 to 7 days for onelevel, while the number of levels that can go up to the time point ofplacing of the underground level mat (for example, the 8th above-groundlevel) and the number of levels that can go up to the completion timepoint (15th above-ground level) of the underground vertical member islimited. Therefore, construction stops and construction waiting occursat an inflection point of the 8th and 15th above-ground levels.

During the construction period of the underground vertical members, itis necessary to achieve a condition that the construction of each levelhas to be carried out continuously and smoothly without temporalflexibility. If even one level is delayed, the above-ground levelconstruction will be delayed by that much. Therefore, the existingconstruction method, in which the underground vertical members have tobe continuously and smoothly constructed in a short period of time, hasa very high risk of delay.

The top-down construction method has an advantage of shortening theconstruction period by constructing the above-ground level whileconstructing the underground level. However, according to the structuralconstraint that the above-ground level cannot go up to more than acertain number of levels depending on the construction speed of theunderground level, the construction period is greatly affected by theconstruction of the underground level frame.

Related applications are as follows.

Application No./Date 1020110024619 (Mar. 18, 2011), Applicant HanbitStructure Engineering Co., Ltd., Registration No./Date 1012420170000(Mar. 5, 2013), Title of Invention Simultaneous construction method ofground and underground structure using ground core pre-construction andlatticed lintel beam in core.

Construction Method

Application No. 1995-0003110, application Date Feb. 18, 1995, Method ofsimultaneously constructing frameworks for floors and underground levelsof a building.

Application No. 10-2003-0037296, application Date Jun. 10, 2003,Simultaneous construction method of building having mixed structure ofreinforced concrete construction and steel framed reinforced concretestructure.

Application No. 10-2011-0087835, application Date Aug. 31, 2011,Registration No. 10-1101182, Registration Date Dec. 26, 2011, Top-downmethod of underground structure.

Application No. 10-2013-0004918, application Date Jan. 16, 2013,Registration No. 10-1426511, Registration Date Jul. 29, 2014, Temporaryskeleton system used in constructing an underground structure of abuilding and a top-down underground construction method using atemporary skeleton system.

SUMMARY OF INVENTION Technical Problem

The present invention was created to solve the problems of the prior artas described above, and an object thereof is to shorten the constructionperiod of the underground vertical members using a top-down constructionmethod so that the above-ground level frame construction can becontinuously carried out. Accordingly, the overall construction periodis shortened.

Solution to Problem

In order to achieve the above object and solve the problems of the priorart, a method for alternately constructing underground vertical membersaccording to the present invention includes alternately constructingunderground vertical members downward, and thereafter, constructing theremaining vertical members during the same time period by beingdistributed between the previously constructed vertical members.

Advantageous Effects

According to the present invention, the following effects can beexpected.

The construction period is shortened by pre-constructing a number ofunderground vertical members on the overall process table and excludingthem from the main process line (critical path) that determines theconstruction period.

By alternately constructing underground vertical members, a bucklinglength of the pillar is shortened, allowing more above-ground levels tobe constructed, thereby shortening the overall construction period.

If the vertical members are alternately constructed, the remainingportions which are constructed upward can be constructed during the sametime period, thereby shortening the overall construction period.

Since the underground vertical members can be constructed early afterthe construction of the corresponding level slab, there is less room forconstruction delay and thereby the overall construction period is notdelayed.

The construction period can be further shortened by constructing onlythe reinforcing bar assembly first and placing concrete during the sametime period.

In the prior art, after placing of the mat, the 6th underground levelvertical member is constructed, and then the 5th underground level, the4th underground level, the third underground level, and the secondunderground level are constructed in a sequence. Accordingly, in theprior art, it took a total of 125 days to construct 5 levels in asequence in a case of 25 days per level. However, according to thepresent invention it takes only 25 days by constructing the 6thunderground level, the 4th underground level, and the second undergroundlevel during the same time period which are the even-numbered levelsafter the mat is constructed because the odd-numbered levels havealready been completed before the mat is placed. As a result, in theprior art, it took 125 days after the mat is placed, but according tothe present invention, it takes 25 days, so that as a result, about 100days are shortened.

According to the present invention, it exhibits an effect of shorteningthe construction period of about 3 months (about 8% of the totalconstruction period) for 36 months compared to 39 months in an officebuilding with 6 underground levels and 39 above-ground levels.

The reduction of the overall construction period in the office andofficetel buildings, and the like reduces construction costs such asconstruction management costs and on-site expenses from the constructioncompany side, and has a high economic effect that early sales, rentalincome, additional sales (25% of annual sales), and the like from thebuilding owner's side.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall flow chart of a method for alternately constructingunderground vertical members according to the present invention.

FIGS. 2 and 3 are examples of process tables of an office building ofthe 39th level in a method for alternately constructing undergroundvertical members according to the present invention.

FIG. 4 is an enlarged process table of an underground vertical memberprocess of FIG. 2 according to the present invention.

FIG. 5 is an example of a process table of the latest start point ofconstruction of the underground vertical members which are alternatelyconstructed according to the present invention.

FIG. 6 is a comparison process table of the earliest start point and thelatest start point of construction of the underground vertical memberswhich are alternately constructed according to the present invention.

FIG. 7 is an overall flow chart of a method for constructing undergroundvertical members of a conventional construction method.

FIGS. 8 and 9 are examples of process tables of an office building ofthe 39th level to which the conventional construction method is applied.

FIG. 10 is an enlarged process table of the underground vertical memberprocess of the conventional construction method of FIG. 8.

FIG. 11 is a comparison process table in which the conventionalconstruction method is compared with the process of the undergroundvertical members alternately constructed according to the presentinvention.

FIGS. 12 and 13 are comparison tables of a schedule difference in whichthe overall process table (FIGS. 8 and 9) of the conventionalconstruction method is compared with the overall process table (FIGS. 2and 3) of the underground vertical members alternately constructedaccording to the present invention.

FIG. 14 is a process comparison graph in which the overall process tableof the conventional construction method (FIGS. 8 and 9) is compared withthe overall process table of the underground vertical membersalternately constructed according to the present invention (FIGS. 2 and3) in an S-Curve form.

BEST MODE FOR INVENTION

Hereinafter, a method for alternately constructing underground verticalmembers using a top-down construction method according to the presentinvention will be described in detail.

FIG. 1 is an overall flow chart of the method for alternatelyconstructing underground vertical members using a top-down constructionmethod according to an embodiment of the present invention. A targetproject to be executed is an SRC office building with 6 undergroundlevels and 39 above-ground levels.

Referring to FIG. 1, in the method for constructing the undergroundvertical members according to the present embodiment, in an earthretaining wall construction step S10, the earth retaining wall isconstructed in the underground level based on an outer wall of theunderground level of the building, and a slurry wall, a CIP, an H-pile,an earth plate, and the like are constructed.

In an underground post construction step S20, pillars of the buildingare constructed from the above ground to the foundation and the mat tosupport a slab of the underground level in the top-down constructionmethod, and a PRD and a RCD are constructed.

In the first level construction slab step S30, the first level slab iscompleted by excavating the first underground level and placing a steelbeam, a deck plate, and concrete using the pillars constructed in thestep S20.

In the first underground level slab construction step S40, the secondunderground level is excavated and the first underground level slab iscompleted as in the first above-ground level.

In the first underground level vertical member (core parts and pillars)construction step S50, the first underground level core parts arecompleted from the first underground level slab constructed in the stepS40, and a core part frame can be constructed upward to the above-groundlevel.

In the above-ground frame (primary) construction step S60, the coreparts and the pillars of the above-ground level are completed from thecore parts and the pillars of the first underground level constructed inthe step S50. For example, if the frame can be constructed up to the 8thabove-ground level before the mat construction under a structuralcondition of a PRD file, in the construction step of the frame (primary)of the above-ground level, the frame is constructed up to the 8thabove-ground level.

In the second underground level slab construction step S70, the secondunderground level slab is constructed after excavating the thirdunderground level downward following the step S40.

In the third underground level slab construction step S80, the thirdunderground level slab is constructed after excavating the 4thunderground level downward following the step S70.

In the third underground level vertical member construction step S90according to the features of the present invention, the thirdunderground level core part is completed from the third undergroundlevel slab constructed in the step S80. After constructing the firstunderground level core part in the step S50, if the construction of thesecond underground level core part is omitted and the third undergroundlevel core part is alternately constructed, the construction can be donein a sequence, thereby making construction easy.

In the prior art, the third underground level core part is constructedin a sequence from the 6th underground level after the mat has beenplaced, but according to the present invention, the third undergroundlevel vertical member is first alternately constructed after the firstunderground level core part is constructed, and thereby the constructionperiod is shortened.

In the 4th underground level construction slab step S100, the 4thunderground level slab is constructed after excavating the 5thunderground level downward following the step S80.

In the 5th underground level slab construction step S110, the 5thunderground level slab is constructed after excavating the 6thunderground level downward following the step S100.

In the 5th underground construction vertical member step S120 accordingto the features of the present invention, the 5th underground level corepart is completed from the 5th underground level slab is constructed inthe step S110. After constructing the third underground level core partin the step S90, if the construction of the 4th underground level corepart is omitted and the 5th underground level core part is alternatelyconstructed, the construction can be done in a sequence.

In the prior art, the 5th underground level core part is constructed ina sequence from the 6th underground level after the mat has been placed,but according to the present invention, the 5th underground levelvertical member is first alternately constructed after the thirdunderground level core part is constructed, and thereby the constructionperiod is shortened.

The third underground vertical member construction step S90 and the 5thunderground vertical member construction step S120 are the method foralternately pre-constructing in a sequence before placing of the mataccording to the features of the present invention, and thereby theconstruction period is shortened.

After that, in the foundation or mat construction step S130, thefoundation and the mat are constructed after the final excavationdownward following the step S110. When the mat is constructed, now theconstruction is turned again and the underground level vertical memberand the above-ground level frame are constructed during the same timeperiod. For example, the above-ground level frame can go up to the 8thabove-ground level before the mat construction, the construction up tothe 15th level can be performed until the construction of theunderground level vertical members are completed, and the constructionup to the roof level, which is the top level, is carried out after theunderground level vertical members are completed.

When the foundation and the mat are completed (S140), the undergroundlevels vertical members (core parts and pillars) are constructed.

Of the underground level vertical members, the first underground levelvertical member (S50), the third underground level vertical member(S90), and the 5th underground level vertical member (S120) werealternately pre-constructed according to the present invention, so theremaining vertical members are in the 6th underground level, the 4thunderground level, and the second underground level. In the presentinvention, for the construction of the remaining vertical members (6thunderground level, 4th underground level, and second underground level),since the core part has already been constructed above and below thecorresponding level, it has an advantage and a feature that theconstruction can be carried out at a time (S150, S160, and S170).

In the prior art, after the 6th underground level core part isconstructed, the 5th underground level core part is constructed, andthen the 4th underground level core part, the third underground levelcore part, and the second underground level core part has to beconstructed in order. However, according to the present invention, sincethe remaining vertical members (6th underground level, 4th undergroundlevel, and second underground level) can be constructed during the sametime period, only one level construction period is required.

Accordingly, before the mat is placed, the core pars of two levels ofthe third underground level and the 5th underground level are firstconstructed, the mat is placed, and then the remaining vertical members(6th underground level, 4th underground level, and second undergroundlevel) are constructed during the same time period, so that an effectthat the pre-construction of a total of 4 levels is carried out isprovided. Therefore, in the prior art, in a case where it takes 25 daysfor the construction of the vertical member of one level, it takes 125days, but according to the present invention, it takes 25 days, andthereby the total construction period of 100 days is reduced.

As described above, when the construction of the underground levelvertical member is completed (S170), construction of the above-groundlevel frame (secondary) (S180) can be started. For example, theabove-ground level frame (primary) can be constructed up to the 15thabove-ground level until the underground level vertical members arecompleted, and after the underground level vertical members arecompleted, the above-ground level frames (secondary) (S180) from the16th above-ground level to the top above-ground level (roof) can beconstructed without restrictions.

FIGS. 2 to 3 are an overall process tables of the method for alternatelyconstructing underground vertical members using a top-down constructionmethod in accordance with an embodiment of the present invention.

Referring to FIG. 2, the present embodiment is carried out in an officebuilding with 6 underground levels and 39 above-ground levels, and hasan SRC structure, and using top-down construction method. Theconstruction start date is Jan. 1, 2019.

Referring to the process table, H-pile/CIP is constructed in the earthretaining wall construction stage (work No. 6 in the first column on theleft of the process table), and the work period is 80 days.

PRD of work No. 7 is provided to construct a number of pillar posts inthe underground level, and the construction period is 70 days.

Excavation of the first underground level and first level slab of workNo. 8 are SRC construction in which the first level floor steel beamsare constructed on posts, and the deck plate and concrete are placedwhen the PRD construction of work No. 7 is completed, and theconstruction period is 50 days.

Excavation of the second underground level and construction of the firstunderground level slab (work No. 9, hereinafter, indicated by only thenumber) are construction in which the second underground level isexcavated downward when the first level slab (No. 8) is completed, andthen the first underground level slab (No. 9) is constructed, and theconstruction period is 50 days.

When the first underground level slab (No. 9) is completed, the firstunderground level core part and the pillar (No. 22) are constructed sothat the construction can proceed to the above-ground level. As aresult, the underground level downward construction and the above-groundlevel upward construction are simultaneously carried out, and this isgenerally referred to as top-down construction.

When the first underground level core part (No. 22) is completed, it ispossible to continuously construct from the second above-ground levelslab (No. 25) to the 8th above-ground level slab (No. 31). At this time,a load on the above-ground level up to the 8th above-ground level isreceived by the PRD.

Since the 9th above-ground slab (No. 32) can proceed only when the matconcrete (No. 15) is constructed, the construction is stopped for about4 months after the construction of the 8th above-ground level (No. 31)is completed. According to a structural calculation, since the PRD canonly support the load up to the 8th above-ground level (No. 31), theconstruction of the 9th above-ground level (No. 32) can be started afterthe mat is placed.

Alternatively, the construction of the above-ground levels from thesecond above-ground level can be started about 3 months late, and thewaiting period of the construction between the 8th and 9th above-groundlevels can be minimized to continuously construct or proceed slowly upto the 8th above-ground level.

When the first underground level slab (No. 9) is completed, the secondunderground level slab (No. 10) is constructed after the thirdunderground level is excavated downward, and the construction period is50 days.

When the second underground level slab (No. 10) is completed, the thirdunderground level slab (No. 11) is constructed after the 4th undergroundlevel is excavated, and the construction period is 50 days.

When the third underground level slab (No. 11) is completed, the thirdunderground level core part (No. 20) is first constructed according tothe features of the present invention. In the existing constructionmethod, the third underground level core part (No. 20) is constructedupward from the 6th underground level after the mat (No. 15) iscompleted. Therefore, according to the present invention, the threeunderground level core part (No. 20) is constructed first compared tothe existing construction method, and thereby the construction period isshortened.

After constructing the first underground level core part (No. 22), thesecond underground level core part (No. 21) is skipped and the thirdunderground level core part (No. 20) is alternately constructed. Thereason is that it is difficult to construct a connection part if thesecond underground level core part (No. 21), which is immediately belowthe first underground level, is constructed in the top-down constructionmethod after the construction of the first underground level core part(No. 22). Therefore, if the third underground level core part (No. 20)is alternately constructed after the first underground level core part(No. 22) is constructed, since the second underground level, which isthe upper level of the third underground level, is empty, the thirdunderground level can be constructed in a sequence, so that theconstruction is easy.

When the first underground level core part (No. 22) and the thirdunderground level core part (No. 20) are alternately completed, thesecond underground level core part (No. 21) disposed between them can beconstructed by sandwiching therebetween.

When the third underground level slab (No. 11) is completed, theconstruction continues downward, and the 4th underground level slab (No.12) is constructed after the 5th underground level is excavated, and theconstruction period is 50 days.

When the 4th underground level slab (No. 12) is completed, the 5thunderground level slab (No. 13) is constructed after the 6th undergroundlevel is excavated, and the construction period is 50 days.

At this time, when the 5th underground level slab (No. 13) is completed,the 5th underground level core part (No. 18) is first constructedaccording to the features of the present invention. In the existingconstruction method, the 5th underground level core part (No. 18) isconstructed upward in order from the 6th underground level after the mat15 is completed. Therefore, according to the present invention, the 5thunderground level core part (No. 18) has the feature of beingconstructed first compared to the existing construction method, andthereby the overall construction period is shortened.

After the third underground level core part (No. 20) is constructed, the4th underground level core part (No. 19) is skipped and the 5thunderground level core part (No. 18) is alternately constructed. Thereason is that the construction of the connection part is difficult toconstruct the 4th underground level core part (No. 19), which isimmediately below the third underground level, using the top-downconstruction method after the third underground level core part (No. 20)is constructed. This is the same as the case of the third undergroundlevel core part (No. 20).

After the 6th underground level is excavated, the mat excavation (No.14) is carried out, and then the foundation and the mat (No. 15) areconstructed.

When the mat (No. 15) is completed, the mat 15 supports the load thathas been supported by the PRD, so that the above-ground level can go upto the 9th level (No. 32) or more.

On the other hand, the reason for limiting that the above-ground levelcan only go up to the 15th level until the completion of the undergroundvertical member after the construction of the mat (No. 15) is thebuckling of the underground level PRD, and the PRD pillars from the 6thunderground level to the second underground level are exposed for about5 levels. However, according to the present invention, since theodd-numbered levels have already been alternately constructed, the PRDpillar is exposed for the height of only one level, so that there islittle buckling restriction. Therefore, depending on the above-groundlevel construction method, a new effect of capable of constructinghigher above-ground levels is exhibited.

After completion of the mat (No. 15), the number of the remaining framesin the underground levels now is three, that is, the 6th undergroundlevel core part (No. 17), the 4th underground level core part (No. 19),and the second underground level core part (No. 21). Since the thirdunderground level core part (No. 20) and the 5th underground level corepart (No. 18) have been alternately completed in advance, the core partsof the remaining three levels may be constructed by sandwichingtherebetween.

According to the features of the present invention, since theodd-numbered level core parts have already been constructed, theremaining three levels can be worked simultaneously, at the same period,or in sequence.

On the other hand, in the construction of the second underground levelcore part (No. 21) and the 4th underground level core part (No. 19),reinforcing bars are pre-constructed, and the concrete is placed duringthe same time period after the mat 15 is placed to further increaseproductivity.

Therefore, in the prior art, three levels (about 75 days) were requiredbecause three levels had to be constructed in a sequence, but accordingto the features of the present invention, since it is possible toconstruct three levels at the same period, the construction period (25days) of only one level is required, so that the effect of shorteningtwo levels is provided because it takes for only one level (25 days).

According to the present invention, the construction period of twolevels is shortened by simultaneously constructing the underground levelvertical members and pre-constructing the third underground level corepart (No. 20) and the 5th underground level core part (No. 18) beforethe mat construction, and the core parts (Nos. 17, 19, and 21) of theremaining three levels are constructed at once after the mat (No. 15) isexcavated to shorten the construction period of two levels, therebyhaving the effect of shortening the construction period of a total offour levels. Since the underground level core part is the mainconstruction line (critical path), the total construction period isshortened.

Referring to FIG. 3, the final work, that is the finishing work, isdisplayed along with the frame construction from the 5th above-groundlevel to the 39th above-ground level. According to the structuralcalculation of the top-down construction, a process table is created inwhich the 9th above-ground level slab (No. 32) can be started after themat is placed, and the 16th above-ground level slab (No. 39) is startedafter all of the underground vertical members are completed. From the16th level to the 39th level of the top level, the construction of theframes is carried out in a cycle of 6 days, and the general finishingconstruction was applied for one year. The finishing constructionincludes interior decoration construction, elevator construction,dismantling of temporary construction such as external curtain wall andtower crane, roof construction, landscaping construction, and the likeafter the roof frame is completed.

Therefore, the total construction period of the office building with the39 levels takes 1,106 days (about 36 months) as illustrated in the workNo. 1 in FIG. 2 when applying the method for alternately constructingunderground vertical members using a top-down construction methodaccording to the present invention. The total construction period isshortened by about 3 months compared to the existing constructionmethod.

FIG. 4 is an enlarged process table of the underground vertical memberprocess of FIG. 2.

Referring to FIG. 4, the construction of the odd-numbered undergroundlevel vertical members (the first underground level core part (No. 22),the third underground level core part (No. 20), and the 5th undergroundlevel core part (No. 18)) among the underground level vertical membersare started after the corresponding level slabs are completed. Theconstruction of the remaining even-numbered vertical members (the 6thunderground level core part (No. 17), the 4th underground level corepart (No. 19), the second underground level core part (No. 21)) of 3levels are carried out at the same period in parallel after the mat 15is placed.

The remaining even-numbered level vertical members (Nos. 17, 19, and 21)have features that can be constructed during the same time period bysandwiching therebetween since the odd-numbered levels have already beenalternately constructed.

FIG. 5 is an example of the process table of the latest start point ofthe underground vertical members that are alternately pre-constructedaccording to the present invention.

The latest start point refers to the work schedule that can beconstructed the latest without affecting the subsequent process. As lateas possible start (finish) time means a schedule that can be constructedthe latest without affecting the subsequent process.

Referring to FIG. 5, the first underground level core part (No. 22) isconstructed after completion of the first underground level slab for theabove-ground level construction (No. 25-). Next, the three undergroundlevel core part (No. 20) can be constructed the latest before theeven-numbered underground vertical members (Nos. 17, 19, and 21) areconstructed.

FIG. 6 is a comparison process table of the earliest start point and thelatest start point of the underground vertical members which arealternately constructed according to the present invention. FIG. 6 isprovided for explaining the contents of the construction which iscarried out at which date or time point in the process table because theconstruction order of the vertical members is determined.

Referring to FIG. 6, work Nos. 16 to 21 indicate an early process (FIG.4), and work Nos. 23 to 28 indicate a late process (FIG. 5). The thirdunderground level core part can be compared through the early work No.20 and the late work No. 27. In other words, referring to the startcolumn in No. 20, the construction of the third underground level can bestarted quickly on Jan. 1, 2020, and can be started on May 15, 2020 inNo. 27. Of course, the construction thereof can be started at any timebetween Jan. 1 and May 15, 2020.

As described above, the idea and embodiments of the method foralternately constructing underground vertical members according to thepresent invention from FIG. 1 to FIG. 6 have been described.

The following describes the construction concept and embodiment of theunderground vertical member of the conventional construction methodusing the top-down construction method in FIGS. 7 to 10.

FIG. 7 is an overall flow chart of the underground vertical memberconstruction method of the conventional construction method using thetop-down construction method.

Referring to FIG. 7, after the earth retaining wall (T10) is constructedon the outside of the building, the PRD or RCD posts (T20) areconstructed underground in order to form frames using the top-downconstruction method. After that, the underground slabs are constructeddownward while excavating the underground levels (T30 to T100). Afterexcavating the 6th underground level (T100), the foundation and the mat(T110) are completed.

Thereafter, the underground vertical members (T130 to T170) areconstructed upward in a sequence from the 6th underground level (T130).

On the other hand, for the above-ground level, after the completion ofthe first underground level core part (T50), the above-ground frame(primary) (T60) is constructed. For example, the construction up to the8th above-ground level slab is carried out until the mat is placed.After placing of the mat, the above-ground level frames (secondary)(T180) from the 9th to 15th above-ground levels are constructed. Whenthe underground vertical members (T130 to T170) are completed, it can beconstructed without restrictions from the 16th above-ground level.

In the conventional top-down construction method, after construction iscarried out downward from the ground to the lowest level, that is, themat is used as a turning point and U-turned to construct the undergroundvertical members upward in a sequence.

Therefore, the order of the underground levels is long, and theunderground construction period is long.

FIGS. 8 and 9 are overall process tables of the top-down constructionmethod to which the conventional construction method is applied.

Referring to FIG. 8, the building is an office building with 6underground levels and 39 above-ground levels, and has an SRC structure,and using the existing reverse construction method of a top-downconstruction method. The construction start date is Jan. 1, 2019. Theconfiguration of FIG. 8 is similar to that of FIG. 2. The reason forexplaining the process table by applying the existing constructionmethod is to examine a difference in the construction sequence and thetotal construction period with the construction method according to thepresent invention.

Referring to the process table, the earth retaining wall constructionstep (work No. 6 in the first column on the left of the process table)is H-pile/CIP work and the construction period is 80 days.

The PRD of work No. 7 is provided to construct a number of pillar postsin the underground levels, and the construction period is 70 days.

Excavation of the first underground level and the first level slabconstruction of Work No. 8 are SRC work that installs the first levelsteel beams on the posts and places the deck plate and concrete when PRDwork of work No. 7 is completed, and the construction period is 50 days.

In the construction of excavation of the second underground level andthe first underground level slab (work No. 9, hereinafter, indicatedonly by the number), when the first level slab (No. 8) is completed, thesecond underground level is excavated downward, and then the firstunderground level slab is constructed, and the construction period is 50days.

When the first underground level slab (No. 9) is completed, the corepart and the pillar (No. 22) of the first underground level areconstructed so that the construction can proceed to the above-groundlevels. Therefore, the underground level downward construction and theabove-ground level upward construction are simultaneously carried out,and this is generally referred to as a top-down construction.

When the first underground level core part (No. 22) is completed, it canwork continuously from the second above-ground level slab (No. 25) tothe 8th above-ground level slab (No. 31). At this time, the load on theabove-ground levels up to the 8th level is supported by the PRD.

Since the 9 level slab (No. 32) can be constructed only when the matconcrete (No. 15) has to be placed, the construction is stopped forabout 4 months after the 8th above-ground level (No. 31) is completed.Since the PRD can only support the load up to the 8th above-ground level(No. 31), it is possible to undertake the 9th above-ground level (No.32) after the mat is placed.

When the first underground level slab (No. 9) is completed, the secondunderground level slab (No. 10) is constructed after the thirdunderground level is excavated downward, and the construction period is50 days.

When the second underground level slab (No. 10) is completed, the thirdunderground level slab (No. 11) is constructed after the 4th undergroundlevel is excavated, and the construction period is 50 days.

When the third underground level slab (No. 11) is completed, theconstruction continues downward, and the 4th underground level slab (No.12) is constructed after the 5th underground level is excavated, and theconstruction period is 50 days.

When the 4th underground level slab (No. 12) is completed, the 5thunderground level slab (No. 13) is constructed after the 6th undergroundlevel is excavated, and the construction period is 50 days.

After the 6th underground level is excavated, the foundation or mat (No.15) is constructed after the mat (No. 14) is excavated. When the mat(No. 15) is completed, since the mat (No. 15) supports the load whichhas been supported by the PRD, so that the above-ground level can go upto the 9th level (No. 32) or more.

When the mat (No. 15) is completed, the underground vertical members(Nos. 17 to 21) are continuously and directly constructed from the 6thunderground level core part (No. 17) to the second underground levelcore part (No. 21), and it takes 25 to 30 days per level. During thisconstruction period, the above-ground level can be constructed from the9th level (No. 32) to the 15th level (No. 38).

Referring to FIG. 9, the 10th to 39th above-ground levels and finishingconstruction are indicated. The process table is created in which theconstruction of the 16th above-ground level slab (No. 39) is startedwhen all the underground vertical members are completed. From the 16thlevel to the top level, the construction of the frames is carried out ina cycle of 6 days without any restrictions on the underground levels,and the general finishing construction is applied for one year.

Therefore, if the method for alternately constructing undergroundvertical members according to the present invention is applied, thetotal construction period of the office building with the 39 levelstakes 1,194 days (about 39 months) as illustrated in work No. 1 of FIG.8.

The total construction period of 39 months is longer by months than thetotal construction period of 36 months according to the presentinvention. The reason is that it takes a lot of time to construct theunderground vertical walls in a sequence from the 6th underground levelto the second underground level.

FIG. 10 is an enlarged process table of the underground vertical memberprocess of the conventional construction method of FIG. 8. Itillustrates that the underground vertical members are constructed in asequence from work No. 17 to work No. 21 after the construction of themat (No. 15), and the construction period is 130 days, that is, it takesabout 4.3 months.

FIG. 11 is a comparison process table in which the process of theunderground vertical members alternately constructed according to thepresent invention is compared with the conventional construction method.

Referring to FIG. 11, work No. 1 to work No 19 are the process tables ofthe conventional construction method, work No. 20 to work No 38 are theprocess tables according to the present invention, and work No. 39 is adifference in construction period between the conventional constructionmethod and the construction method of the present invention.

First, in the conventional construction method, from work No. 12 to workNo 16, the five underground level core parts (No. 10) are constructed ina sequence after construction of the mat (No. 10), and it takes 130days.

On the other hand, according to the present invention, from work No. 31to work No 35, only 30 days are required after construction of the mat29, and thereby it indicates that the construction period is shortenedby 100 days in the present invention (No. 39).

The reason is that the third underground level core part (No. 34) andthe 5th underground level core part (No. 32) are previously constructed,and the remaining three level core parts (Nos. 31, 33, and 35) can beconstructed by inserting each other simultaneously or at the same timepoint (at the same period) after the construction of the mat 29. Afterodd-numbered level core parts are constructed, the remainingeven-numbered level core parts are constructed at once. As a result, theconventional construction method requires construction of 5 times.However, in the present invention, the effect of shortening 100 days of4 levels with construction of only one time is exhibited

FIGS. 12 and 13 are comparison tables of a schedule difference in whichthe overall process tables (FIGS. 8 and 9) of the conventionalconstruction method are compared with the overall process tables (FIGS.2 and 3) of the underground vertical members alternately constructedaccording to the present invention.

Referring to FIG. 12, the total construction period difference (workNo. 1) in the two construction methods is 88 days of about 3 months,that is, it takes about 39 months in the conventional constructionmethod and 36 months in the construction method of the presentinvention, and it can be seen that about 8% of the total constructionperiod is shortened.

The underground excavation, the top-down slab, and mat construction(Nos. 6 to 15) are the same in the construction period in bothconstruction methods.

The difference therebetween occurs from the underground verticalmembers, and according to the present invention, the undergroundvertical members (core parts) are alternately constructed downward, andthe construction of the remaining core parts is carried out at the sametime.

The last column (I) is a value obtained by subtracting the completiondate for each level (column E) of the existing construction method fromthe completion date for each level (column H) according to the presentinvention.

From the 16th above-ground level (No. 39), the difference of 88 days isfixed and continues until construction is completed.

FIG. 13 illustrates that the schedule difference (completion datedifference column (I)) of 88 days continues from the 16th above-groundlevel (No. 39) until the completion of the construction.

FIG. 14 is a process comparison graph in which the overall processtables (FIGS. 8 and 9) of the conventional construction method arecompared with the overall process tables (FIGS. 2 and 3) of theunderground vertical members alternately constructed according to thepresent invention by indicating in an S-Curve form from FIGS. 12 and 13which are arranged in tables.

Referring to FIG. 14, a blue line indicates the existing constructionmethod, and a red line indicates the construction method of the presentinvention.

Construction is started on Jan. 1, 1999, and the 6th underground levelmat is placed on Jun. 8, 2020 (lowest point in the graph).

Thereafter, the red line according to the present invention indicatesthat two levels are already alternately constructed, and three levelsare constructed during the same time period in one month to complete theunderground vertical members, and then lead to the 16th level.

On the other hand, the blue line according to the conventionalconstruction method indicates that it takes about 4.3 months toconstruct the underground vertical member for each level after the matconstruction, and then leads to the 16th level. From the 16th level andabove, the two construction methods are the same.

As described above, the differences between the existing constructionmethod and the construction method of the present invention are comparedthrough the process tables and the graph.

The following is a description of a case where some work is performeddifferently in embodiments of the present invention.

In construction of a case where the final excavation is the 5thunderground level, the underground core parts are first constructeddownwards on the first and third underground levels, and after the matis completed, the 5th underground level is constructed, and then the 4thand second underground levels may be constructed during the same timeperiod. Therefore, after the mat construction, the remaining core partsare constructed twice.

In construction of a case where the final excavation is the 4thunderground level, the underground core parts are first constructeddownward on the first and third underground levels, and after the mat iscompleted, the 4th and second underground level core parts can beconstructed during the same time period. It is the same concept as theconstruction of the 6 underground levels.

Since the level height of the lowest underground level is not high, thelowest two levels (for example, the 5th and 6th underground levels) maybe simultaneously excavated, the mat be completed, and then the 5thunderground level slab be constructed. In this case, aftersimultaneously constructing the 6th underground level core part and the5th underground level slab, the 5th underground level core part isconstructed. Therefore, after the mat construction, the remaining coreparts are constructed twice.

As described above, in a case of simultaneously excavating two levelswith odd numbered levels or the lowest two levels, it occurs in someconstruction that the remaining core parts are constructed twice in asequence after the mat is completed. Therefore, according to oneembodiment of the present invention, after alternately completing thecore parts, there are many cases where the remaining core parts arecompleted at once, and in some construction, a case of constructing theremaining parts twice is derived.

The process table of the above embodiment is an example in which thedate calculation is accurate because it is prepared by a programspecializing in process table preparation. The Kant chart, which is ared bar chart in the process table, represents a major operation thatdetermines the total construction period as a critical path of the majorprogress line. The blue bar chart represents an operation with float inthe number of temporal flexible dates. Therefore, in order to shortenthe construction period, the red line, which is the main constructionline, has to be shortened. A connection line (relationship) includingarrows connecting the bar charts in the process table indicates thepreceding and subsequent relationship between works.

As described above, according to the features of the present invention,based on the idea of alternately completing the core parts in order toshorten the construction period of the underground core parts, whichdetermines the overall construction period, it can be seen that theremay be some derivative core part construction in a sequence depending onthe features of the site. However, unlike the sequential core partconstruction method which is the existing construction method, engineersin the construction industry clearly know that the core partconstruction method partially modified based on the idea of shorteningthe overall construction period through the alternate core partconstruction method according to the present invention is included thegist of the present invention.

MODES FOR CARRYING OUT THE INVENTION

This is the sequence of the method for alternately constructing verticalmembers using a top-down construction method in a case of 8 undergroundlevels according to an embodiment of the present invention.

The construction sequence is as follows.

Earth retaining wall

Underground pillars (PRD, RDC, and ACT pillar)

Excavation of the first and second underground levels

Placing of the reinforced concrete of the steel deck in the firstunderground level (placing of slab)

Excavation of the third underground level

Placing of the second underground level slab, and placing of the firstunderground level core wall pillar

Excavation of the 4th underground level

Placing of the third underground level slab

Excavation of the 5th underground level

Placing of the 4th underground level slab, and placing of the thirdunderground level core wall pillar

Excavation of the 6th underground level

Placing of the 5th underground level slab

Excavation of the 7th underground level

Placing of the 6th underground level slab, and placing of the 5thunderground level core wall pillar

Excavation of the 8th underground level and excavation of the mat

Placing of the 7th underground level slab, placing of the core wallpillar of the 7th underground level

Placing of the 8th Underground Level Mat

Placing of the remaining levels of 8th underground level, 6thunderground level, and 4th underground level, and the core wall pillarof 4th underground level (simultaneous construction of 4 levels)

Alternatively, after primary construction of 2 levels of the 8thunderground level and added one level, secondary construction of thecore wall pillars of 2 levels (construction of 2 levels twice)

Alternatively, after primary construction of 2 levels of the 8underground level and added one level, secondary and tertiaryconstruction of the core wall pillars of the remaining 2 levels one byone (construction of total 3 times of 2 levels once, and 1 level twice)

Alternatively, after construction of the core wall pillar of the 8thunderground level, construction of the remaining 3 levels one by one(construction of total 4 times for 4 levels)

After placing of the mat, the remaining levels are 4 levels, and the 4levels are placed by dividing into 1 time, 2 time, 3 time, and 4 time.

The followings are the sequence of the method for alternatelyconstructing vertical members using a top-down construction method in acase of 7 underground levels according to an embodiment of the presentinvention.

Earth retaining wall

Underground pillars (PRD, RDC, and ACT pillar)

Excavation of the first and second underground levels

Placing of the reinforced concrete of the steel deck in the firstunderground level (placing of slab)

Excavation of the third underground level

Placing of the second underground level slab, and placing of the firstunderground level core wall pillar

Excavation of the 4th underground level

Placing of the third underground level slab

Excavation of the 5th underground level

Placing of the 4th underground level slab, and placing of the thirdunderground level core wall pillar

Excavation of the 6th underground level

Placing of the 5th underground level slab

Excavation of the 7th underground level and excavation of the mat

Placing of the 6th underground level slab, placing of the 5thunderground level core wall pillar

Placing of the 7th underground level mat

In the remaining levels of the 7th underground level, the 6thunderground level, the 4th underground level, and the second undergroundlevel

After primary construction of 2 levels of the 7 underground level andadded one level, secondary construction of the core wall pillars of theremaining 2 levels

Alternatively, secondary construction of the 7th underground level and 2levels among the remaining 3 levels, and construction of the remaining 1level (construction by dividing total 3 times)

Alternatively, construction of total 4 times one level by one level

The followings are the sequence of the method for alternatelyconstructing vertical members using a top-down construction method in acase of 6 underground levels according to an embodiment of the presentinvention.

Earth retaining wall

Underground pillars (PRD, RDC, and ACT pillar)

Excavation of the first and second underground levels

Placing of the reinforced concrete of the steel deck in the firstunderground level (placing of slab)

Excavation of the third underground level

Placing of the second underground level slab, and placing of the firstunderground level core wall pillar

Excavation of the 4th underground level

Placing of the third underground level slab

Excavation of the 5th underground level

Placing of the 4th underground level slab, and placing of the thirdunderground level core wall pillar

Excavation of the 6th underground level and mat

Placing of the 5th underground level slab and placing of the mat

Placing of the 6th underground level mat and placing of the 5thunderground level core wall pillar

In the remaining levels of the 6th underground level, the 4thunderground level, and the second underground level

Simultaneous construction of the remaining 3 levels (total 1 time)

Alternatively, after construction of the 6th underground level,simultaneous construction of the 4th underground level and the secondunderground level (total 2 times)

Alternatively, after simultaneous construction of the 6th undergroundlevel and the 4th underground level, construction of the secondunderground level (total 2 times)

Construction of 3 levels one level by one level for total 3 times(construction by dividing into 3 times).

The followings are the sequence of the method for alternatelyconstructing vertical members using a top-down construction method in acase of 5 underground levels according to an embodiment of the presentinvention.

Earth retaining wall

Underground pillars (PRD, RDC, and ACT pillar)

Excavation of the first and second underground levels

Placing of the reinforced concrete of the steel deck in the firstunderground level (placing of slab)

Excavation of the third underground level

Placing of the second underground level slab, and placing of the firstunderground level core wall pillar

Excavation of the 4th underground level

Placing of the third underground level slab

Excavation of the 5th underground level, and excavation of the mat

Placing of the 4th underground level slab, and placing of the thirdunderground level core wall pillar

Placing of the 5th underground level mat

In the remaining levels of the 5th underground level, the 4thunderground level, and the second underground level

After construction of the 5th underground level, simultaneousconstruction of the 4th underground level and the second undergroundlevel (total 2 times)

Alternatively, after simultaneous construction of the 5th undergroundlevel and the second underground level, construction of the 4thunderground level (total 2 times)

Construction remaining 3 levels one level by one level (total 3 times).

The followings are the sequence of the method for alternatelyconstructing vertical members using a top-down construction method in acase of 4 underground levels according to an embodiment of the presentinvention.

Earth retaining wall

Underground pillars (PRD, RDC, and ACT pillar)

Excavation of the first and second underground levels

Placing of the reinforced concrete of the steel deck in the firstunderground level (placing of slab)

Excavation of the third underground level

Placing of the second underground level slab, and placing of the firstunderground level core wall pillar

Excavation of the 4th underground level and excavation of the mat

Placing of the third underground level slab and placing of the 3thunderground level core wall pillar

Placing of the 4th underground level mat

In the remaining levels of the 4th underground level and the secondunderground level

Simultaneous construction of the remaining 2 levels (total 1 time)

Construction of 2 levels one level by one level (total 2 times).

INDUSTRIAL APPLICABILITY

Currently, most of the top-down construction is carried out in downtownconstruction. With respect to the alternately constructing methodaccording to the present invention, first, a structural design officedesigns the method, a contractor manufactures the steel frame and theformwork, and then the construction is carried out. Therefore, thepresent invention can be directly applied industrially.

1. A construction period shortening method through a method foralternately constructing underground vertical members in construction ofunderground vertical members of a building in which an above-groundframe is constructed upward in parallel with construction of anunderground structure downward, comprising: a first step of excavatingand constructing an underground level slab downward; a second step ofalternately pre-constructing an underground vertical member; and a thirdstep of constructing remaining underground vertical members alternately,during the same time period, or in 2 times after the construction of thesecond step, wherein the construction is alternately carried out.
 2. Theconstruction period shortening method through a method for alternatelyconstructing underground vertical members according to claim 1, whereinwhen the underground level is a 6th underground level, first undergroundlevel, 3rd underground level, and 5th underground level core parts arealternately pre-constructed while constructing the underground slabdownward, and then 6th underground level, 4th underground level, and 2ndunderground level core parts are constructed during the same timeperiod.
 3. The construction period shortening method through a methodfor alternately constructing underground vertical members according toclaim 1, wherein when the underground level is a 5th underground level,first underground level and 3rd underground level core parts arealternately pre-constructed while constructing the underground slabdownward, and then the 5th underground level core part is constructed,the 4th underground level core part is constructed, and the secondunderground level core part is constructed during a construction periodof the 5th underground level and the 4th underground level.
 4. Theconstruction period shortening method through a method for alternatelyconstructing underground vertical members according to claim 1, whereinwhen the underground level is a 4th underground level, first undergroundlevel and 3rd underground level core parts are alternatelypre-constructed while constructing the underground slab downward, andthen the 4th underground level and second underground level core partsare constructed during the same time period.
 5. The construction periodshortening method through a method for alternately constructingunderground vertical members according to claim 1, wherein when 2 levelsof the lowest level of the underground levels and an upper level thereofare simultaneously excavated, the core parts are alternatelypre-constructed while constructing the underground slab downward, themat or the foundation is constructed, the lowest level core part and anupper level slab thereof are constructed, and then the remaining coreparts are constructed during the same time period.
 6. The constructionperiod shortening method through a method for alternately constructingunderground vertical members according to any one of claims 1 to 5,wherein the core parts, which are alternately pre-constructed, and theremaining core parts, which are constructed thereafter during the sametime period, are constructed by dividing into preceding and subsequentbased on the mat excavation work.
 7. The construction period shorteningmethod through a method for alternately constructing undergroundvertical members according to any one of claims 1 to 5, wherein aconstruction schedule of each of the core parts, which are alternatelypre-constructed, is in a range between an earliest possible start date(early start date) which starts after the completion of thecorresponding level slab and the latest completion date (late finishdate) which is completed before a time point when the remaining coreparts are constructed subsequent.
 8. The construction period shorteningmethod through a method for alternately constructing undergroundvertical members according to any one of claims 1 to 5, wherein theunderground vertical member includes a core part or a pillar connectedto an above-ground level.
 9. The construction period shortening methodthrough a method for alternately constructing underground verticalmembers according to claim 1, wherein in the alternately constructedunderground vertical members, the core part or the pillar of theodd-numbered (or even-numbered) underground level is pre-constructedwhile constructing the underground slab downward, the mat or thefoundation is constructed, and then the core part or the vertical memberof the pillar of the even-numbered (or odd-numbered) level, which is theremaining level, is constructed at once or twice depending on siteconditions.
 10. The construction period shortening method through amethod for alternately constructing underground vertical membersaccording to claim 1, wherein the construction of the remaining coreparts subsequent and at once further includes a method for placingconcrete, which is a subsequent process, at the same period afterinstalling a reinforcing bar of the remaining underground core part asearly as possible.
 11. A construction period shortening method through amethod for alternately constructing underground vertical members,comprising: (a) a step of constructing a temporary earth retaining wallin a ground by a conventional method; (b) a step of verticallyinstalling an above-ground level core part and pillar, from aboveground, which is constructed upward in parallel with construction of aunderground structure downward when the underground structure and theabove-ground structure are constructed; (c) a step of excavating thefirst above-ground level, constructing a floor part thereof, excavatingthe first underground level, and then constructing a floor part thereof;(d) a step of excavating each of the remaining underground levels inorder in a downward direction and constructing the floor part, andsimultaneously constructing core parts of one underground level or aplurality of underground levels first to support the above-ground levelcore part which is preferentially constructed upward; (e) a step ofpreferentially constructing the above-ground level core part in anupward direction on an upper part of the underground level core partwhich is constructed first, and installing the underground level framein the downward direction in parallel therewith; (f) a step ofalternately installing the core parts after the core part of oneunderground level is installed first in the step of installing theunderground level frame in the downward direction; (g) a step of formingthe foundation after the underground level frame is completed to thefoundation, and installing the core parts of the remaining levels to bealternately constructed downward in the upward direction from the lowestlevel to the underground level core part which is constructed first,during the same time period or sequentially; and (h) a step ofconstructing the construction completion through the remaining frameconstruction of the above-ground level and the final construction thatis finishing work, wherein the underground core parts are constructedfirst or during the same time period within a certain possible range toexclude them from a main process line critical path to shorten anoverall construction period.
 12. The construction period shorteningmethod through a method for alternately constructing undergroundvertical members according to claim 11, wherein the step of alternatelyinstalling the core parts includes constructing the odd-numbered levelcore part, the remaining level core parts include the even-numberedlevel core parts, the odd-numbered level and even-numbered level coreparts are converted based on the mat construction, and the lowest levelcore part and the upper level core part thereof are sequentiallyconstructed depending on site features.